Orthodontic applicance with radiused wire slot

ABSTRACT

A set of orthodontic brackets is provided in combination with an archwire extending over an arc when fitted to the set of orthodontic brackets. The archwire has at least one radius of curvature over the length of its arc, and each one of said brackets in the set has an archwire slot. Each slot has at least one surface supporting the archwire which is contoured to have a radius of curvature that matches the radius of curvature along the arc of the archwire at that point. A round archwire is preferred and the archwire slots may be formed as tubular channels to provide better torque action for the archwire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of pending U.S. patentapplication Ser. No. 13/568,594 filed Aug. 7, 2012, which is acontinuation-in-part of pending patent application no. PCT/US2011/024067filed Feb. 8, 2011, and is related to and claims priority from pendingGerman application DE 10 2010 008 749 filed Feb. 20, 2010.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to orthodontic appliances and in particular, toorthodontic brackets having a curved archwire slot that is round incross section.

Description of Related Art Including Information Disclosed Under 37 CFR1.97 and 1.98

Orthodontic treatments for the repositioning of teeth employ acombination of appliances that are affixed to the teeth and archwires,which are coupled to the appliances. By placing the correct amount oftension on the archwires, the orthodontist is able to manipulate theposition and orientation of a patient's teeth.

Orthodontic appliances, also known as “brackets” each possess anarchwire slot, which accommodates an archwire. The archwire is a pieceof stiff wire that has a curve that approximates the arc of the teeth ina human mouth. That is, from the rear molars of the left side of themouth to the rear molars on the right side of the mouth, there is anatural curve that forms an arc of about 180 degrees. The arc is notcircular but U-shaped. At the distal ends, the arc barely has any curveat all and is mostly straight. As the arc approaches the front teethhowever, its curve becomes more pronounced.

To properly adjust the tension of the archwire, it is necessary that theinteraction of the archwire in each archwire slot be as free fromextraneous forces as possible. The torque that a properly adjustedarchwire places on teeth acts in an inward/outward direction, normal tothe surface of the tooth. Forces that act in a side-to-side direction,that is, along the arc of the archwire itself, are undesirable. Suchforces can be present, however, because the ends of the archwire slotshave edges that contact the archwire and act as a resistance to themovement of the archwire in the slot. This can be the case in locationsin the mouth where the curve of the archwire is most pronounced. In somecases, the archwire rests almost entirely across opposite edges of theslot, which results in an unacceptable amount of friction as those edgesdig in to the wire. Tightening the archwire then leads to moments withforces directed in undesirable directions.

Archwires may be either round or rectangular in cross section. Arectangular archwire gives more control to the orthodontist, but alsopresents problems. Rectangular archwires in rectangular slots producefriction. Each surface in the slot is a bearing surface that can producefriction and retard desired application of forces. In certain phases ofthe treatment, it may be advantageous to use one type versus the other.For example, the end phases of treatment frequently call for the use ofa round archwire. Round archwires are chosen for this phase becausethere is less friction between a round wire and an archwire slot.However, archwire slots are made rectangular to accommodate rectangularor square archwires. Round archwires are commonly used in rectangular orsquare slots but this arrangement is less desirable than it could be.There is still friction produced by the round archwire engaging thestraight walls of the slot. Additionally, round archwires do not torquewell in rectangular slots because of the lack of contact between thewire and the walls of the slot.

Typically, orthodontic brackets have profiles that cause irritation ofthe inner lip surfaces of a patient because the bracket is rectangularin cross section and its edges protrude too far above the top of thetooth. Typical orthodontic bracket designs are shown in various U.S.patents such as Wildman et al. (U.S. Pat. No. 5,613,850), Damon (U.S.Pat. No. 5,466,151) and in published application no. US2004/0072117 toFarzin-Nia et al. (now U.S. Pat. No. 7,419,375).

BRIEF SUMMARY OF THE INVENTION

An orthodontic appliance is applied to the top surface of a tooth andincludes a base portion and an upper portion, the upper portion having aslot to receive an archwire. The slot is curved to match the radius ofcurvature of the archwire and is round in cross section to permit theuse of round archwires.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view of a tooth correction means formed of aplurality of tooth top parts and a connecting means.

FIG. 2 is a lateral view of a first embodiment of a tooth top part in afunctional position.

FIG. 3 is a perspective view of the tooth top part according to FIG. 2.

FIG. 4 is a schematic view of the tooth top part according to FIGS. 2and 3.

FIG. 5 is a lateral view of a second embodiment of a tooth top part in afunctional position shown as solid lines and in an assembly positionshown as dotted lines.

FIG. 6 is a lateral view of a third embodiment of a tooth top part in afunctional position.

FIG. 7 is a perspective view of another embodiment of a low profilebracket.

FIG. 8 is a top view of the bracket of FIG. 7.

FIG. 9 is a cutaway side view taken along line 9-9 of FIG. 9 with anarchwire shown in dashed outline.

FIG. 10 is a cutaway view taken along line 10-10 of FIG. 8.

FIG. 11 is a top view of the brackets of FIG. 8 installed on a patient'steeth in dashed outline and connected by a power chain.

FIG. 12 is a side cutaway view of the brackets of FIG. 11.

FIG. 13 is a bottom view of a patient's mouth showing a set oforthodontic brackets attached to teeth and an archwire spanning thebracket set.

FIG. 14 is a top view of a prior art bracket featuring a rectangulararchwire slot.

FIG. 14A is a cutaway view taken along line A-A of FIG. 14

FIG. 14B is a cutaway view taken along line B-B of FIG. 14

FIG. 15A is a top view of an orthodontic bracket having a roundedarchwire slot and a round archwire.

FIG. 15B is a perspective view of the bracket of FIG. 15A.

FIG. 16 is a side view of the archwire and bracket of FIG. 15A.

FIG. 17 is a cutaway view of the archwire and bracket of FIG. 15A takenalong line 17-17 of FIG. 15.

FIG. 18 is a cutaway view of the archwire and bracket of FIG. 15A takenalong line 18-18 of FIG. 15A.

FIG. 19 is a cutaway view of the bracket of FIG. 17 attached to apatient's tooth.

FIG. 20 is a top view of a preformed archwire attached to fiveorthodontic brackets.

FIG. 21 is an enlarged view of the archwire of FIG. 20 and two of theattached brackets.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

One aspect of the invention relates to a tooth top part for a toothcorrection means, with a base body at which a tooth support surface isformed for being fixed at a tooth surface by bonding, and which isprovided with a guide recess which is formed for receiving a connectingmeans for coupling neighboring tooth top parts and which passes throughthe base body in spaced relationship to the tooth support surface alonga guiding axis.

A tooth top part of this type, which is also referred to as a bracket,is known from DE 20 2009 008571 U1. The known tooth top part is formedat an outward-facing surface of a tooth for being fixed by bonding, andto that end comprises a tooth support surface which is used as anadhesive surface for adhesively attaching (adhering) the tooth top partto the surface of the tooth. The tooth top part is provided with agroove-type recess extending along a guiding axis and being spaced fromthe tooth support surface. The known tooth top part comprises asubstantially H-shaped cross section in a cross sectional plane normalto the guiding axis. The recess in the tooth top part permits insertionof a connecting means, which couples tooth top parts attached toneighboring teeth and permits transmission of forces between the teeth.The forces and, if applicable, the torques transmitted by the connectingmeans enable the teeth to move relative to each other and permitcorrection of false positioning (malocclusion) of teeth.

The tooth top part known from the prior art has a drawback that theH-shaped cross section, which may be approximated by a rectangularenvelope (curve) in the cross sectional plane causes irritations of themouth mucous membrane (oral mucosa) in particular at the inside of thelips. This results in reduced wearing comfort for a tooth correctionmeans formed by a plurality of such tooth top parts.

It is an object of the invention to provide a tooth top part thatcomprises improved adjustment to the anatomical conditions in the mouthregion and thus causes less irritation of the mucous membranes.

This object is achieved in a tooth top part as mentioned in the aboveintroduction using the features of claim 1 which provides that the basebody comprises a substantially triangular or circular section shapedcross section in a cross sectional plane normal to the guiding axis.

The triangular or circular section shaped cross section guaranteesreduced friction during relative movements between the tooth top partsand the opposing mucous membrane. Thus, due to the reduced friction, themucous membranes will be irritated less both during talking and foodintake, and discomfort caused by sore spots in the mucous membrane isreduced. Preferably, compared to known tooth top parts, these tooth topparts have a reduced overall height, which may provide a furtherreduction in mucous membrane irritations. Preferably, the height of thetooth top part in a direction normal to the tooth surface is less than2.5 times, in particular less than 2 times, the largest edge length (forinstance with a rectangular cross section) or the diameter of theconnecting means. More preferably, the connecting means comprises alargest edge length or a diameter selected to be less than 0.5 mm, inparticular less than 0.4 mm.

Further advantageous embodiments are presented in the sub-claims.

Appropriately, a base line of the substantially triangular or circularsection shaped cross section is formed by the tooth support surface, anda mean perpendicular to the base line comprises a length less than 50percent of the length of the base line. With this shape of the profileof the tooth top parts, an advantageous ratio is achieved between thesize of the tooth support surface required for secure immobilization ofthe tooth top parts at the tooth surfaces and the height of therespective tooth top part. The length of the mean perpendicularcorresponding to the maximum height of the tooth top part beyond thetooth surface is small compared to known tooth top parts. As a result,when combined with the triangular or circular section shaped crosssection of the tooth top part, a particularly gentle use of the toothcorrection means constituted with the tooth top parts according to theinvention can be achieved.

Preferably, each of the outer surfaces of the base body, adjacent to thetooth support surface, include acute angles, preferably less than 45degrees, more preferably less than 35 degrees, particularly less than 25degrees, with the tooth support surface. The outer surfaces of the toothtop part are those surfaces at the base body that are in particularlyintensive contact with the opposing mucous membranes of the mouthregion. The smaller the selected angle between the outer surface and thetooth support surface, the greater the wearing comfort of the toothcorrection means constituted by the tooth top parts. However, sincereception of the connecting means is always required, the angles cannotbe reduced at will.

The triangular cross section of the base body may be formed as anisosceles triangle having identical acute angles between the two outersurfaces and the tooth support surface. Alternatively, the triangularcross section may be formed as a triangle at will where the acute anglesincluded between the respective outer surface and the tooth supportsurface are selected differently. The circular section shaped crosssection may be selected as a symmetrical or asymmetrical circularsection.

In a further improvement of the invention, transitional regions betweenthe outer surfaces and/or between an outer surface and the tooth supportsurface are formed with a rounding-off radius. This avoids sharp edgesat the transitions between the outer surfaces or between the outersurface and the tooth support surface which too could give rise tounwanted mucous membrane irritations.

Appropriately, the, preferably undercut, guide recess is formed as agroove-type indentation starting from one of the outer surfaces of thebase body. A groove-type indentation enables comfortable and rapidinsertion and, if required, removal of the preferably wire-shapedconnecting means into the guide recess and from the guide recess,respectively. This is particularly true if the groove opening of theguide recess extends alongside the guiding axis of the guide recess,thus enabling insertion/removal of the connecting meanscrosswise/transverse to the direction of its overall extension.Preferably, the guide recess is formed with an undercut that, forinstance, allows the connecting means to be locked within the guiderecess.

Advantageously, at least one, preferably sectionally elastic, snap-onnose is formed at the base body, said snap-on nose regionally limitingthe groove-type indentation and being formed for lockingly receiving theconnecting means in the guide recess. The snap-on nose is meant toimmobilize the connecting means at the tooth top part such that, on onehand, the latter is able to transmit the desired forces between adjacentteeth and, on the other hand, can be easily attached at the tooth toppart and, if required, removed again therefrom. Preferably, the snap-onnose is formed as an at least sectionally elastic spring nose enablingsnap-in of the connecting means and self-locking, in particular positivelocking (form-locking), immobilization of the connecting means at thetooth top part. Alternatively, the groove-type recess may also be closedusing a separate locking element or a locking element integrallyattached to the base body, wherein the locking element may, forinstance, be shifted or swung/pivoted between a locked position and anopen position.

In an advantageous improvement of the invention, the snap-on nose isformed for self-locking, in particular positive locking (form-locking),immobilization of the connecting means at the base body. With aself-locking design of the snap-on nose, the connecting means is pushedinto the tooth top part while being elastically deformed and, whenreaching a predetermined functional position, will be immobilized solelyby the resilience (elastic restoration properties) of the snap-on nosewithout any effort by the user. Preferably, the connecting means, theguide recess in the tooth top part and the snap-on nose are coordinatedsuch that immobilization of the connecting means by positive locking isachieved.

Preferably, the base body is made of a preferably tooth-colored, clearor translucent synthetic material (plastics material). This enables thetooth top parts to be inconspicuously arranged within the mouth regionof a patient. More preferably, the tooth top parts are formed indifferent colorings and/or degrees of transparency in order to allow forlow contrast adaptation to the respective tooth color.

Appropriately, the groove-type indentation is formed for lockinglyreceiving a profiled connecting means that is formed for transmittingtorsional forces between neighboring tooth top parts. This enhances theversatility of the tooth correction means made of the tooth top partsaccording to the invention by the possibility of inducing pivotingmovements between neighboring teeth. More preferably, the connectingmeans comprises a square or rectangular cross section, which is at leastpartially mapped in the recess of the tooth top part in order to allowthe transmission of torque between the connecting means and the toothtop part.

In an advantageous improvement of the invention, the groove-typeindentation is adapted to the connecting means such that a, preferablylow friction or nearly zero friction, relative movement of theconnecting means with respect to the base body, in particularalong/alongside the guiding axis of the recess is enabled. This allowsparticularly rapid correction of false positioning of teeth withoutrequiring frequent readjustment of the connecting means. The mentionedcoordination between the recess and the connecting means is alsoreferred to as self-ligating, since the connecting means is free to movein the recesses of the tooth top parts in accordance with the patient'sneeds without requiring any additional elements such as rubber rings forimmobilizing the connecting means at the tooth top parts.

Preferred embodiments of the invention are shown in the drawings.

In a human tooth arrangement schematically shown in FIG. 1 andcomprising molars, canines and incisors, a tooth correction means 1according to the prior art is shown in the left-hand region of FIG. 1,whereas a tooth correction means according to the invention is shown inthe right-hand region of FIG. 1. Both tooth correction means are used inorder to achieve a desired arrangement of the teeth with respect to eachother. The tooth correction means 1 comprises several tooth top partswhich, as an example, are attached at tooth surfaces 3 of all teeth andwhich are coupled to each other by a connecting means 4 for instancehaving a wire shape. The connecting means 4 enables the transmission offorces and, if required, also torques between the teeth in order tobring the teeth in a predeterminable position during orthodontictherapy. In the prior art tooth correction means, the tooth top partsclearly extend further from the teeth and the wire thickness of theconnecting means is clearly selected to be thicker.

As can be seen from FIG. 2, the tooth top part 2 according to theinvention, which is identical to the base body in the presentembodiment, comprises a tooth support surface 5 by means of which it isbonded to the tooth surface 3 in a known manner. The tooth supportsurface 5 is flanked by a first outer surface 6 and a second outersurface 7 each of which includes an acute angle 18, 19 (FIG. 4) with thetooth support surface 5. Transitional regions between the outer surfaces6, 7 and the tooth support surface 5 are formed with a rounding-offradii 20, 21.

In the shown embodiment of the tooth top part 2, end faces 8, 9 of thetooth top part 2 are orthogonal to the outer surfaces 6, 7 and to thetooth support surface 5. Thus, the end faces 8, 9 in the shownembodiment of the tooth top part 2 are parallel to a cross-sectionalplane identical to the drawing plane of FIGS. 2 and 4.

As can be seen from the schematic view of FIG. 4, a cross section of thetooth top part 2 is formed such that it is contained within a triangularenvelope 11 or within a circular section shaped envelope 11 a. A meanperpendicular 14 of the envelope 11 is orthogonal to a base line 13 ofthe envelope 11, determined by the tooth support surface 5. A length ofthe mean perpendicular 14 is less than 50 percent, in the presentexample about 40 percent, of the length of the base line 13, whichresults in a low profile for the tooth top part 2, thus causing lessirritations of the mouth mucous membrane (not shown).

In the embodiment of a tooth top part shown in FIGS. 2 through 4, arecess 12 extending normally to the cross sectional plane 10 is providedwith a substantially L-shape profile. For instance, the tooth top part 2is formed as a geometrically extruded component having a constant crosssection normal to the cross sectional plane la throughout its length.Thus, the recess 12 also extends with a constant cross section and thus,determines a guiding axis 17 coinciding with a central axis of the forinstance wire-shaped connecting means 4 having a circular cross section.

Due to the substantially L-shaped profile design, a snap-on nose 15 anda snap-on hook 16 for immobilizing/securing the connecting means areformed in the base body 2 of the tooth top part. The snap-on nose 15 isdesigned for locking the connecting means 4 in the shown functionalposition within the snap-on hook 16, thus guaranteeing a safe, positivelocking (form locking) immobilization of the connecting means 4 at thetooth top part 2 crosswise/transverse to the extension of the connectingmeans 4. During an assembly operation (not shown), where the connectingmeans 4 is pushed transversely to its longitudinal extension into therecess 12, both the snap-on nose 15 and the snap-on hook 16 undergoelastic deformation. During the assembly operation, while the snap-onnose 15 is bent toward the tooth support surface 5, the snap-on hook 16undergoes deformation in the opposite direction. As a result, the recess12 opens up a cross section enabling insertion of the connecting means4. As a result of a preferably exclusively elastic deformation of thesnap-on nose 15 and the snap-on hook 16, the tooth top part isself-locking for the connecting means 4.

As soon as the connecting means 4 arrives at the functional positionshown in FIGS. 2 through 4, the resilience, i.e., elastic restorationforces, of the snap-on nose 15 and the snap-on hook 16 will have anon-positive locking (force locking) and positive locking (form locking)effect for forces occurring within the cross sectional plane la withoutrequiring any additional measures to that end. Both the snap-on nose 15and the snap-on hook 16 comprise elastic regions formed as solid-statejoints enabling elastic pivoting into the assembly position andrestoration into the functional position.

In a variant of the tooth top part 2, the snap-on hook 16 may bereinforced using an insert 22, preferably made of an elastic/resilientmetal, as shown in FIG. 4.

In the following description of a second embodiment of a tooth top part22 shown in FIG. 5, components with identical function are givenreference numerals increased by 20. The tooth top part 22 is providedfor receiving a connecting means 24 having a rectangular cross sectionin the present case and which enables the transmission of torque betweenneighboring tooth top parts 22. The recess 32 is adapted to theconnecting means 24 such that the latter engages the snap-on hook 36 viathree lateral surfaces and is pressed by the snap-on nose 35 into thisregion of the recess 32.

As can be seen from the dotted-line representation of FIG. 5, when theconnecting means 24 is mounted, the snap-on nose 35 is 10 supposed to bebent downward while the snap-on hook is deformed downward toward thetooth support surface 25. This causes the recess 32 to open up a crosssection through which the connecting means 24 can be brought into thefunctional position, as it exists in the solid-line representation ofFIG. 5. After the connecting means 24 has reached the functionalposition, the snap-on nose 35 and the snap-on hook 36 will pivot backelastically into the initial position shown with solid lines and thus,will cause positive locking (form locking) of the connecting means.

Demounting of the connecting means 24 can be effected by holding downthe snap-on nose 35 toward the tooth support surface 25 with a tool (notshown) and subsequently pivoting the connecting means 24 out of therecess 32 by performing a pivoting movement while deforming the snap-onhook 36.

A simplified embodiment of a tooth top part 42 is shown in FIG. 6. Inthis case, the cross section of the recess 52 substantially correspondsto the cross section of the connecting means 44 and is only limited bybarbed hooks 57 provided on both sides in the region of the grooveopening. These barbed hooks 57 are elastically displaced when theconnecting means 44 is inserted into the recess 52, and will move backinto the shown position as soon as the connecting means 44 has reachedthe functional position. The advantage of the embodiment according toFIG. 6 can be considered as having no hollow spaces at the tooth toppart 42 due to the corresponding cross sections of the connecting means44 and the recess 52. Demounting of the connecting means 44 ispreferably effected by pulling it out laterally toward the guiding axisoriented normally to the drawing plane of FIG. 6.

The tooth top parts 2, 22, 42 shown in FIGS. 2 through 6 are preferablymade of a synthetic material such as a plastics material. Alternatively,the use of ceramics or metal for producing the tooth top parts ispossible. In doing so, it may be necessary to modify the geometries ofthe tooth top parts, in particular in the region of the solid-statejoints, in order to guarantee the desired elastic properties. When usingsynthetic materials such as plastic materials or ceramic materials forthe tooth top parts, a regional/sectional reinforcement employing metalinserts may be provided.

The tooth top part 2, 22, 42 according to the invention enables relativedisplacement and/or pivoting of neighboring teeth. Given that the toothtop part 2, 22, 42 does not have any hooks and eyelets (no “nooks andcrannies”), no additional connecting elements such as rubber bands canbe inserted. In order to provide for additional force application to theteeth to be corrected, additional hooks may be provided in the region ofthe gum line. These additional hooks, which may be attached in astructurally separated manner from the tooth top parts 2, 22, 42 atselected or all teeth and which are preferably made of syntheticmaterial, enable additional connecting elements to be hooked up whichare typically significantly shorter than the tooth top parts 2, 22, 42and, as they are suited exclusively for hooking up additional connectingelements, can be designed in a very skinny fashion. By providingadditional hooks in the region of the gum line, these hooks as well canbe placed very inconspicuously and in particular at particularlysuitable force application points on the teeth to be moved, since thiswill favor parallel displacement of the teeth. Due to the decoupling ofthe different force application systems, which are determined by thetooth top parts 2, 22, 42 on one hand and by the additional hooks on theother hand, not only an optically inconspicuous attachment of thecorresponding components for the tooth correction means with littleirritation of the mouth mucous membrane, but also a particularlyefficient movement of the teeth due to the advantageous selectability ofthe force application points can be achieved.

In another aspect of the invention, a bracket 100 as shown in FIGS. 7-11includes a base 102 and a top portion 104. The brackets 100 are affixedto teeth 101 (shown in dashed outline). The base 102 has a width in boththe gingival-occlusal plane (L1) and a length in the distal-anteriordirection (W1). The top portion 104 is made of an elastically deformablehook portion 106 that curls around past the apex to create asubstantially cylindrical or tubular archwire channel 108. Note that theinterior of this channel could also be rectangular in cross section asshown in the embodiment of FIG. 6. In this embodiment, the snap-on noseis eliminated and a shelf 110 is formed underneath the hook portion 106.The shelf and the distal end of the hook portion 106 form an opening 112that is slightly smaller than the largest diameter of an archwire 114(dashed outline in FIG. 9). When the archwire 114 is press fitted intothe opening 112, the hook portion 106 elastically deforms allowing thearchwire to enter the channel 112. Once the archwire 114 has reached itsfunctional position, the hook snaps back, securing the archwire 114therein. The archwire may be removed by prying the hook portion 106upward with a tool (not shown).

The archwire 114 for this bracket is thin. Treatment typically beginswith an archwire having a diameter of 0.010″. It progresses during thetreatment to 0.012″ and eventually to 0.014″. All archwires fit withinthe bracket 100, which has a nominal channel diameter of 0.016″. Asshown in FIG. 12, the archwire channel is larger in the center portionof the bracket for reducing friction.

The archwire has a radius of curvature “R” as also shown in FIG. 12. Theinterior shape of the hook portion (and hence, of the archwire channel108) of the top part in the distal-anterior direction is curved and hasa radius of curvature made to match the radius of curvature “R” of thearchwire. This insures that the archwire slides through the channel withthe least amount of friction possible.

The base and the top portion may be configured to provide a tie wing foran elastic power chain 120. An elastic power chain (see FIG. 1) is anelastic band with at least two open loops 122 joined by bridge portions124. The power chain 120 has three loops and can be looped aboutadjacent brackets so as to exert a compressive force tending to drawthem together as shown in FIG. 11. The power chain may have any numberof loops desired.

To form a tie wing, the top portion 104 is made longer in thedistal-anterior direction than the width of the base 102 in this samedirection as shown in FIG. 8 by the arrows designating W1 and W2. Inaddition, the base 102 may be chamfered at its corners so that the powerchain 120 is retained more easily when it is looped over the top of thebracket. The corners 130, 132, 134 and 136 are all chamfered to providea surface for retaining the power chain loops 122.

The bracket 100 is a small low-profile bracket in which the mean height“h” is less than half of the length L1 of the base 102 in thegingival-occlusal direction. The low profile insures that the bracketwill not irritate the inside of the lips of the patient. Typicaldimensions are that the gingival-occlusal length of the base is about0.135″. Thus, the bracket could be 0.140″ to 0.130″ inches in length.The low profile comes from the height of the bracket, which in apreferred embodiment is about 0.053″, but could range, preferably, fromabout 0.048″ to 0.058″. The height of the bracket, however, should notexceed half of the gingival-occlusal length. Thus if the length were0.130″, the bracket height should not exceed 0.065″. This results in abracket that is triangular in cross section with a rounded crown at theapex. The triangle is a shallow low-profile shape that makes the bracketcomfortable for the patient and is easy to adjust.

Referring to FIG. 13 an archwire 200 is coupled to brackets 202 whichare affixed to a patient's teeth. The archwire is curved over its lengthin the mesial-distal direction in a horseshoe shape as viewed in thegingival-occlusal plane but the curvature is not constant. At the distalends at the buccal tubes 204, 205 the archwire 200 is nearly straightalong the molars 203. The radius of curvature begins to change fairlyabruptly at the bicuspids 206, 207, the cuspid 208 and curves across thelateral 209 and the central 210. There may be different radii ofcurvature in the archwire at different points along its length.

In a prior art bracket as shown in FIGS. 14, 14A, 14B, a rectangulararchwire 211 spans the archwire slot 212 of a typical bracket 213. AsFIG. 14A shows, when there is curvature in the archwire 211, it contactsthe ends of the slot 212 and does not lie flat. Thus, the ends of theslot dig into the archwire at these points and resist lateral slidingmovement.

In the embodiment of the bracket of FIGS. 15A-18, a round archwire 220occupies an archwire slot 222 in a bracket 224, which has two portions,slot portion 222 a and portion 222 b. The archwire slot portions arerounded U-shaped channels having straight walls and are curved at thebottom to form a tubular channel having a radius that matches the radiusof the archwire at least approximately. The slot portions are formedbetween each pair of tie wings 219, 218. There is a gap 217 between thetie wings 218, 219 so that the archwire makes contact only with slotportions 222 a and 222 b. This reduces the amount of lateral slidingfriction between the archwire 222 and the archwire slot 222. Over 180degrees of the outer surface of the archwire are in direct contact withthe walls and bottom of the archwire slot portions 222 a, 222 b. Thus,forces directed inwardly, normal to the tooth, or in theocclusal-gingival directions are well coupled to the bracket 224. Thisis illustrated in FIG. 19, which shows how torque may be coupled to apatient's tooth by way of an archwire 220 in a rounded bottom archwireslot 222.

This property also exists in the low profile brackets of FIGS. 7-12. InFIG. 9, the archwire slot or channel 108 is round in order toaccommodate the round archwire 114. The archwire 114 only contacts thechannel 108 at either end of the bracket. Thus, friction is reduced dueto the expanded radius in the middle of the bracket where the archwiredoes not touch.

Archwires are Nickel-Titanium and are heat treated to retain theirshape. They thus have memory and tend to return to their original shape,which has been chosen and fashioned for optimal results. This springeffect generates forces that are applied to the walls of archwire slots.With round archwire slots, forces are coupled in the desired directionmore efficiently because for over more than half of the circumference ofthe archwire the surface is in direct contact with the slot, whichefficiently couples the return forces to any contact point within thearchwire slot.

Referring to FIG. 18, the archwire slot 222 of the bracket 224 has aradius of curvature that matches the radius of curvature of the archwireslot 222 at that position. The floor of the archwire is formed with aconvex curvature that may be different for different brackets, dependingupon where along the curve of the archwire 220 they are placed. Forexample, referring to FIGS. 20 and 21 the curvature of each respectivearchwire slot, 231, 233 is different for brackets 230 and 232. The radiiof curvature may vary depending upon the size and shape of the archwire220. The table below gives ranges of values that are typical for mostcommon shapes and sizes of archwires.

Tooth Position Radius Range in Inches Upper 1 0.85-2.20 Upper 20.75-2.00 Upper 3 0.75-2.00 Upper 4 3.00-7.50 Upper 5 3.00-7.50 Lower 10.70-2.00 Lower 2 0.70-2.00 Lower 3 0.50-2.00 Lower 4 2.50-7.50 Lower 52.50-7.50

These values are merely typical and may change depending on the size andshape of the archwire. Moreover, each bracket in a set will have its owncontoured archwire slot depending upon its position in the mouth. Thus,a set of values exists for radii of curvature for individual archwireslots in a set of brackets.

The use of a contoured archwire slot is applicable to any type oforthodontic bracket including the low profile brackets of FIGS. 1-12 orthe generic full size brackets of FIGS. 13-21. The same is true of therounded archwire slots. The use of round wires in complementarilyrounded archwire slots is advantageous in any type of orthodonticbracket.

The terms and expressions that have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

We claim:
 1. A combination, comprising a set of orthodontic brackets andan archwire, each said bracket having an archwire slot with a basesurface that is in contact with and supports said archwire, saidarchwire adapted to bear against said base surfaces and thereby applypressure to a patient's teeth to correct malocclusions, the archwireextending lengthwise in a mesial-distal direction, and forming an outersurface having at least one first radius of curvature along saidmesial-distal direction, and a second radius of curvature along adirection substantially perpendicular to said mesial distal direction;said base surfaces of said archwire slots having at least one thirdradius of curvature along said mesial distal direction, said at leastone third radius of curvature substantially congruent with said at leastone first radius of curvature, such that said base surfaces of saidarchwire slots are in contact with said archwire over a curved,contiguous mesial-distal length of said archwire when said set oforthodontic brackets and said archwire are assembled together, and saidbase surfaces of said archwire slots having a fourth radius of curvaturealong a direction perpendicular to said mesial distal direction, saidfourth radius of curvature substantially congruent with the secondradius of curvature such that said base surfaces of said archwire slotsare in contact with said archwire over a curved, contiguous arc in aplane perpendicular to said mesial distal direction, when said set oforthodontic brackets and said archwire are assembled together.
 2. Thecombination of claim 1 wherein each said bracket is configured toselectively, snapably receive and retain said archwire in said archwireslot.
 3. The combination of claim 2 wherein each archwire slot comprisesa hook portion and a nose portion.
 4. The combination of claim 3 whereineach of the hook portion and the nose portion are elastically deformableto snapably receive and retain the archwire.
 5. The combination of claim4 wherein the hook portion and the nose portion are configured suchthat, when the archwire is inserted into the slot, the hook portion andthe nose portion elastically deform in opposite directions relative toeach other.